Custom firmware for a 3-key + rotary encoder macropad.

Forked from biemster/3keys_1knob, which is based on wagiminator/CH552-Macropad-mini.

Compared to original, keypresses are generated on key release, to allow key combinations.

Also, layer and combination support is added, and sending multimedia (consumer) keycodes.

$ make bin

• if on original firmware: connect P1.5 to GND and connect USB
  • alternate method, on some boards: USB- to 3.3V, using 10k resistor
• if on this firmware: press key1 while connecting USB
  • alternate method: press and hold all three keys
• $ make flash

1. $ make get_isp (first time only)
2. $ make dump
3. edit flashdata.bin (for example with hexedit)
4. $ make data

Layers 1, 2, 3 and have the same layout. Layer 1 starts at 33, and so on. Max layers exists only on layer 0. On others, this value can be used as delay, if layer is used as sequence (delay will be value * ~100 ms).

• MMCC - four bytes, key settings
  • MM - modifier:
    • if set to 0xFF, character code will be sent as Consumer Keyboard Keycode
      • also, character codes 0xF0 - 0xFB (0xFFF0-0xFFFB) allow layer manipulation.
    • otherwise, modifier keys bits in order: (7) RG RA RS RC LG LA LS LC (0)
    • R - right, L - left, C - ctrl, S - shift, A - alt, G - gui (win)
  • CC - keycode (ASCII, or from usb_conkbd.h)
    • also layer manipulation, when MM is set to 0xFF:
      • 0xF0-0xF3: set layer to 0-3,
      • 0xF5-0xF8: set max layer to 0-3,
      • 0xFA: switch to layer -1,
      • 0xFB: switch to layer +1.
      • 0xFD: print current layer as 1 character.
• MM and CC - encoder pressed settings are split into two halves
  • this indicates settings for when encoder is pressed down and then turned
  • it is active only when layers are disabled (max_layers set to 0)
• RRGGBB - 24-bit colour, byte for red, green and blue:
  • foreground - layer colour, used when switching, and after switch has been pressed,
  • background - default level, foreground will fade out to it,
  • fade - fade step, each loop removes these values from current level, until background level is reached,
• max layers - NN - 0-3 controls keyboard behaviour, as explained below.

As data memory is very limited, some tradeoffs had to be made.

This keyboard can operate in four different modes, as selected by max layers value.

• 0 - only layer 0 is active, but each key can use up to four keys in sequence.
  • first key from layer 0 will be pressed, then from 1, 2, and 3
• 1 - layers 0 and 3 will be active. Up to three keys on layer 0, and one on 3.
  • layer 0 will press keys from 0, 1, and 2
• 2 - layers 0, 2, and 3 active, layer 0 uses keys from 0 and 1, in sequence.
• 3 - all layers are active, no sequences available, only one keypress per layer.

To switch between layers:

• press and hold encoder's switch to switch to layer 0,
• assign keycodes from group 0xFFF0-0xFFFF to switch to other layers.